Can a gunfight happen when only one person has a gun?
Languages are not Math, they are a Being, they are life... You must not think a word means only what a dictionnary tells you; words mean what people want them to mean, (and then when a high amount of people give them the same meaning, they acquire it). If you want that the 2+ people must have a gun, then call it that way, if not, call it "pseudogunfight".
Be creative, words are magic! =)